1. Field of the Invention
The present invention relates to an apparatus for spinning a yarn from natural and/or synthetic staple fibers, particularly to a friction spinning apparatus comprising a yarn formation surface, a fiber feed duct for conveying fibers onto the surface, means for moving the surface to twist the fibers deposited thereon to form a yarn and means for withdrawing the yarn transversely to the direction of motion of the surface.
2. Description of the Related Arts
In a known type friction spinning apparatus, the fibers are fed into a throat formed between the adjacent peripheral surface of two parallel drums rotating in the same direction. By friction contact with the moving drum surfaces, the fibers in the throat are twisted into a yarn which is then withdrawn transversely of the movement of the drum surfaces.
One of the most serious problems with the above type friction spinning apparatus is that the fibers supplied to the throat are deposited unsatisfactorily in the region of the tail end of a fiber bundle being spun for incorporation therein.
To solve this problem, an apparatus is proposed in U.S. Pat. No. 4,315,398, in which, besides a suction stream by which the fibers are held on the drum surface, an additional air stream is generated by means of a suction source in the direction generally parallel to the yarn axis and at a location adjacent the twisting surface in a fiber feed duct arranged to feed the fibers directly onto the area from which the yarn is withdrawn, whereby part of the fibers are stretched along the yarn axis and the correct deposit thereof into the yarn is enhanced (see FIG. 14). This apparatus, however, has drawbacks in that a considerable amount of effective fibers is sucked out by the additional stream causing the increase of waste and, further, the fibers tend to deposit at a turning point of the stream on the inner wall of the fiber feed duct.
Another apparatus is proposed in German Patent Publication DOS No. 27 20 625, as shown in FIGS. 12 and 13, in which fibers fed through a fiber feed path to a yarn formation surface are intermittently beaten by a disc with a sawtooth periphery, which disc is rotating in a plane perpendicular to the flying direction of the fibers, while the tip end of the saw teeth thereof is inserted into the fiber feed duct through a guide wall confining the fiber feed path. The fibers are thrown toward a means for withdrawing the yarn formed on the yarn formation surface, whereby the orientation of the fibers is improved to be parallel to the yarn axis. This apparatus, however, is sophisticated and liable to malfunction due to the provision of the rotating disc which requires a driving means associated therewith.